This invention relates to a broadcast signal recording and playback apparatus and method as well as a recording medium, and more particularly to a broadcast signal recording and playback apparatus and method as well as a recording medium suitable for use to record or play back, for example, a television signal in which a CM (commercial message) is included.
Where a television broadcast signal is received and recorded into a recording and playback apparatus for an AV signal such as a video tape recorder, a CM is detected in order to play back the television broadcast signal skipping only CM portions or to record the television signal except CM portions.
Conventionally, a CM is detected making use of the facts that generally a sound absence period for approximately 0.1 second to 2 seconds appears with a high probability at a start point and an end point of each CM, that a scene changing point of an image is present within a sound absence period, the time required for each CM is an integral number of times 15 seconds and the audio mode in a CM broadcasting period is a stereo mode as seen in FIGS. 1A to 1D.
In particular, if a scene changing point within a sound absence period appears after an interval of time equal to an integral number of times 15 seconds and a stereo audio is broadcast within a period cut out with a time length of an integral number of times 15 second, it is discriminated that the period is a CM period.
An example of configuration of a conventional CM detection apparatus is shown in FIG. 2. Referring to FIG. 2, a sound absence period in an audio signal included in a broadcast signal is detected by a sound absence detection section 1 while a scene change in a video signal included in the broadcast signal is detected by a scene change detection section 2. Then, a CM in the broadcast signal is detected by a CM detection section 3 based on the sound absence period detected by the sound absence detection section 1 and the scene change detected by the scene change detection section 2. The audio signal and the video signal are multiplexed and recorded onto a recording medium not shown. A result of the CM detection by the CM detection section 3 may be recorded onto the recording medium together with a stream of the AV signal or may be recorded into a memory such as a semiconductor memory different from the recording medium on which the AV signal is recorded.
Upon recording, CM detection is performed and a result of the detection is recorded. Then upon playback, an AV signal is played back, for example, with a CM skipped based on the recorded result of the CM detection.
Since such an algorithm as described above is conventionally used to detect a CM, the conventional CM detection is disadvantageous in that, if the AV signal has a pattern which complies with the algorithm, then the portion of the AV signal is detected as a CM in error even if it is not a CM period.
The conventional CM detection is further advantageous in that it cannot detect a rarely found CM which does not have a pattern which complies with the algorithm.